Summary

As the southern winter begins in Mayotte, the COVID-19 epidemic continues throughout the territory. The department remains in a state of high vulnerability given the circulation of the virus and the direct and indirect impacts of the epidemic on the population’s health. The arrival of the dry and windy season marks the end of the dengue epidemic, which the department had been facing since late 2019. For three months, this dual epidemic complicated the daily work of healthcare professionals, as the symptoms were similar. Laboratory tests and medical imaging then aided in diagnosis. The population also bore the brunt of this exceptional health situation, with nearly 4,500 cases of dengue and about 40 documented cases of co-infection.

To describe and understand the epidemiological dynamics of COVID-19, several surveillance systems were implemented by Santé publique France (SpF) in collaboration with its partners. The collected data enable monitoring of the epidemic’s progression and assessment of its severity. Epidemiological analysis helps guide decision-makers in adapting the strategy to combat the epidemic.

Fifteen weeks after the first case was detected on the island, epidemiological indicators are declining but remain at a relatively high level, as evidenced by the overall incidence rate (47 cases per 100,000 inhabitants) and the positivity rate for SARS-CoV-2, which is around 20%. These data must be interpreted with caution given the biases introduced by variability in healthcare utilization, specimen collection, diagnosis, and testing practices. Thus, it is likely that the scale of the current epidemic is underestimated.

As of June 24, 2020, 2,467 cases of COVID-19 had been confirmed by the CHM laboratory and the island’s private laboratory. These facilities can perform up to 200 tests per day when testing supplies are available. To date, more than 10,000 PCR tests have been conducted, corresponding to 8,883 individuals tested. Since mid-June, laboratories have been able to perform qualitative detection of IgG antibodies against SARS-CoV-2. To date, given the uncertainties surrounding the immunity conferred by infection, the use of serology remains limited to specific situations. This test has been used, in particular, to determine the origin of suspected severe cases of Covid-19 admitted to intensive care or to confirm post-infectious syndromes.

In Mayotte, the severity of the epidemic has been relatively low. Indeed, while sixty-three cases were admitted to intensive care with a diagnosis of COVID-19, barely more than half of them were hospitalized for a severe pulmonary form of the disease. Thus, for one in four patients, the infection was discovered incidentally. Finally, 11 cases presented with myocarditis, including 5 children and 6 adults. This phenomenon is currently under surveillance. In total, 34 deaths have been recorded since the start of the epidemic, though a causal link to COVID-19 infection has not been established.

Viral circulation continues in a pattern that is difficult to pinpoint. Indeed, the proportion of the population exposed to the virus remains unknown. Only a seroprevalence study would allow for an assessment of the situation in Mayotte, though it would not provide answers regarding immunity. This uncertainty necessitates maintaining vigilance regarding preventive measures, in a context where general lockdown is no longer in effect.

Thus, adhering to preventive measures remains a daily challenge for residents and must be facilitated by secure access to a water source. Furthermore, since individual susceptibility and exposure to infection are two factors that can vary considerably from one individual or population group to another, every individual and every social group can help limit the risk of an epidemic. Indeed, wearing masks and maintaining physical distancing during close contact are practical tools for preventing person-to-person transmission. Similarly, local officials are responsible for allocating concrete resources to prevent the emergence of outbreaks in situations conducive to close and prolonged contact, particularly in enclosed spaces. Particular vigilance will therefore be required in the period leading up to Sunday, June 28, when many Mahorians will go to the polls for municipal elections. These will likely be followed by celebrations that encourage gatherings.

Consequently, early detection and monitoring of clusters must continue to ensure the implementation of immediate control measures. To date, one cluster in a healthcare facility remains under surveillance, as does the prison cluster. The fourteen other identified clusters are now under control thanks to the systematic isolation of cases, the identification and quarantine of contacts, and the implementation of expanded testing operations.

Currently, the testing strategy remains unchanged in Mayotte: any patient presenting with symptoms suggestive of COVID-19 must undergo diagnostic testing. Now more than ever, access to diagnostic and screening tests remains one of the key measures in the fight against the epidemic: combined with the systematic isolation of cases, it should enable a better understanding of the epidemic’s dynamics and the early containment of transmission chains. Discussions are currently underway to organize the systematic screening of contacts around a case, as proposed by the national strategy.